Mattress and method for reducing stress concentration when supporting a body

ABSTRACT

The present invention is an improved mattress or cushion enclosed in a functional membrane that relates to the controlling of flexible, rigid or visco-elastic foam, springs, air, fluids, particulates, combinations thereof and foam density variations to meet varying force support needs, as well as other support means that have employed surface technology to modify the basic support characteristics and the interface created therefrom with a supported body in a manner intended to support the body optimally. One potential non-health-related result of the implementation of the present invention is to save national need for petroleum-based products, forestry and expenses attributed to shipping with complicated interface support methods normally incurred as a shipping expense without a reusable feature.

CITATION TO PRIOR APPLICATION

This is a CONTINUATION-IN-PART with respect to U.S. application Ser. No. 10/665,059, from which priority is claimed under 35 U.S.C. § 120.

BACKGROUND OF THE INVENTION

1. Field of The Invention

The present invention generally relates to mattresses. More specifically, the present invention relates to improved mattress, cushion and packaging material encased in a functional membrane that uniquely reduces stress concentrations when supporting a human or other body.

2. Background Information

The human body can tolerate many forces, but one part of the body subjected to continuous forces is the outer covering of skin or “tissue.”

When one walks, one generally hardens the underside of the feet through intermittent pressure, abrasion and shear exerted by their body mass against the earth's gravity. The underside of the feet, as well as the hands and elbows, are made of special underlying tissue to be able to withstand these forces and grow calluses, whereas the underside of the arm is tender and not designed for such loading.

Similarly, the tissue over the posterior (back) of the heels, lateral trochanters (hipbones), ischial tuberosities (sit-bones), malleolus (ankles), iliac crest (waist), scapula (shoulder blades), ears and occiput (back of the head) are thinly covered, poorly vascularized and cannot tolerate “loading” as well as the feet and hands.

The noted bony areas are primarily sharp compared to the feet, except, of course, the head or where underlying bony spurs are established. Thus, when a load is applied to these surfaces, one momentarily retracts from that load in an effort to protect the trauma being applied to the tissue. However, without good sensation at the surface of the tissue to send signals to the brain for counteraction, one cannot respond appropriately and “tissue trauma” results or skin is damaged. When exceedingly high forces are applied, the pressure or shear adjacent to the applied force is sufficient to damage the tissue integrity, which is referred to as a “cut” or “needle stab” and in dire situations, tissue is actually torn apart by explosion, impact, machinery accidents, etc. But, there is another form of tissue damage that is similar to the development of blisters that occurs when tissue has been over-stressed and the outer covering may break. This results in usually minor tissue damage, but can extend itself to a major “sore” ischemic ulcer or “bedsore” if countermeasures are not immediate.

Exacerbating this situation is the normal aging process and deterioration of normal body functions. Upon aging, tissue is not as viable as younger tissue. Sensory feedback, which carries signals regarding tissue viability information back to our brain, is no longer as rapid and there is the potential of tissue harm due to the unawareness of tissue failure. Especially prone to this situation are those with diabetes, spinal cord injuries, leprosy, overdose, dementia and so on, as well as the elderly, whose tissue no longer has the turgor to counteract minor inflictions on its surface.

A person who is elderly or has some enervation and is confined to bed for an extended period will have a propensity to develop tissue trauma sores (ischemic ulcers, decubitus ulcers or bedsores). Typically these sores appear over bony prominences where forces arising from the weight of the body are concentrated and the lack of movement leads to tissue destruction. (Those with normal sensation and mobility become uncomfortable and move to a different position, while those under anesthetics can't move). To avoid such sores, some form of tissue pressure/shear interface should be provided to reduce these forces to a value that the tissue can tolerate.

To better understand why the tissue dies, a simple example is to push a finger hard onto a flat surface. Immediately, pain can be perceived. The tissue is being forced up the side of the finger bone, under the outer tissue, and the tissue is “shearing” away from the bone. Directly at the center of that finger bone is the “peak” pressure with adjacent tissue being applied “average” pressure. Again, the average pressure may thus be low and the peak pressure very high and this is why “average” pressure readings found in various products and interface pressure studies does not give correct tissue interface pressure information for protection of that tissue.

This peak pressure eliminates nutrient passage to the stressed tissue area and the tissue dies when the load is sustained. This peak pressure phenomena is also related directly to comfort but average pressure is not, as reported in the article “Body Support Testing and Rating” in Hospital Materiel Management Quarterly, Volume 14, number 1, August 1992 by Aspen Publishers wherein sixteen different configurations of mattresses were tested and rated.

These tissue trauma forces may be adjusted in a number of ways—i) by putting the load where the body can tolerate it, ii) by attempting to control interface forces across the patient body support surface, or iii) by moving the patient periodically before tissue reaches an irreversible death situation.

There have been many efforts, as evidenced by patents discussed below, to eliminate this problem by a means other than nursing help, which has resulted in a plethora of equipment claiming to reduce the incidence of so-called Pressure Ulcers, or more correctly known as “Ischemic Ulcers,” as they are caused by factors other than just “pressure”.

The magnitude of this problem can best be described as “horrific.” It is estimated that in 1989 1.7 million hospitalized patients were afflicted with the above scenarios. The average cost for each patient was $40,000 to repair and settlements in the $250,000 range. Additionally, it is estimated that the United States spends $7-$55 billion per year on this preventable problem, while mortality rate for the afflicted patients is between 23 and 37%. About half of all patients over 70 years of age developing these ulcers have a fourfold increase in the rate of death. More expenses are hidden, e.g., when comparing patients with bedsores (Ischemic Ulcers) to those without bedsores, the average length of stay increased by a factor of five.

DESCRIPTION OF PRIOR ART

In recent years, inventors have approached this problem of tissue breakdown prevention using two basic approaches for body support, fluidic substance or polymeric foam. Each of these methods encompasses many variations that have met with differing degrees of success. Also of note and in most instances, cross-contamination or dust mite prevention has not been considered as part of a performance requirement until after-the-fact.

1. Fluidic Support

Water/Air. Making use of a shaped structure and air bladders was proposed by Weinstein et al. in U.S. Pat. No. 3,456,270 wherein water was the supporting medium and a lifting inflatable bladder interface was used for raising patient for transfer.

Whitney in U.S. Pat. No. 3,802,004 changed a patient immersion depth through unique bladder arrangements inflated by air, without changing medium volume.

Hagopian in U.S. Pat. Nos. 5,072,468 and 5,068,935 describes a special bed frame for ease of manufacture and the use of water as the base medium with an air bladder on its upper surface to lower or raise the patient, as in Reswick (later), with the added ability to provide an inflated wedge for postural trunk control of the patient.

These approaches also were an attempt to reduce “hammocking” over bony prominences that tends to negate the efficacy of the support medium. It should be noted that the modern waterbed is comprised of water, a supporting envelope to “hammock” some one so that they do not sink into the bed and appropriate baffling or channeling for stability of the water.

Air. There are a number of ways in which air has been compressed, blown or applied to support a patient. Hart in 1926 in U.S. Pat. No. 1,772,310, described a technique of alternating the fluidic support points on the body by controlling the time each support point was to be activated, while limiting interface pressure to an acceptable value. Hart also introduced a method of patient turning in this same patent.

Whitney, in U.S. Pat. No. 3,148,391 used a modified method of support that was compact and introduced temperature control of interface as well as the alternating method of support.

Ford in U.S. Pat. No. 4,711,275 opted to inflate and deflate arrays of air cells through independent air compressors to create an alternating pressure support system.

Krouskop in U.S. Pat. No. 4,989,283 opted to control height of the supporting bladders in his approach to body support by measuring any changes in cell configuration through a microprocessor using its input from internal bladder sensors to control appropriate valving to pressure sources or exhausts to maintain each bladder at some referenced height.

Others used lateral support tube shaping (Talley of the UK), while others included an air loss to circumvent needle puncturing problems (3M) with appropriate control mechanisms.

Air, as a fluidic support, has been proposed in many forms for various purposes of body positioning. A surgical table is the subject of Canadian Patent 1035000 by Carrier where individual bladders of air are positioned to keep the bony prominences clear of the table, while providing a fairly stable support as each bladder is independently inflated to a desired pressure. All are then covered by a forgiving cover.

Air cushion machines are quite effective in supporting a large unforgiving body against a homogenous and somewhat stiff undersurface; however, their use as a patient support medium is impractical. Then again, if enclosed in a container of soft tough and highly flexible material, air is much more suitable for patient support if designed correctly to reduce hammocking.

Consequently, by using air in tubular or oval containers and arranging appropriately within the bed frame, a mattress of air tubes is a reasonable approach, depending on cross sectional area of bladders and their positioning. Shaping these air tubes and putting holes in them to circumvent accidental needle punctures and with a pump sufficiently large to keep ahead of the leak rate, had its merits.

Although Armstrong, U.S. Pat. No. 2,998,817, first developed an inflatable massaging and “cooling” system, as time passed, materials were developed that had built in leak rates suitable for beds and, thus, the current Low-Air Loss mattress approach evolved using so-called vapor-permeable materials. Such materials may consist of 80 denier nylon, or thereabouts, backed with a material of choice such as a film of urethane or vinyl.

Hess, U.S. Pat. No. 4,638,519, demonstrated use of shaped bladders using such materials with appropriate individual bladder control and methods of bladder attachments with air supplies while Goode, U.S. Pat. No. 4,797,962, used the process of controlling these air bladders in groups as a means of modifying support pressure under portions of the body as others have done in the aforementioned. (Some of these approaches have been prone to collapse when the patient is in the sitting position in the bed, and consequently exposing the coccyx and ischial tuberosities [sit bones] to excess pressure and shear due to increased bladder loading by the vertical component of the trunk.)

Some have attempted to reach suitable body support through the use of foam on top of slats placed on top of air cylinders, as outlined by Wilkinson, in U.S. Pat. No. 5,070,560.

High Density Fluid. Reswick, in U.S. Pat. No. 3,803,647, used a mixture of Barium sulfate ore and water (or other fluids) as a medium of support with a loose fitting lifting interface sheet as the top member of the unit. This sheet was inflated and allowed access to the patient at a suitable working height for the attendant personnel. The aqueous solution of barites was used as its specific gravity could be much greater than “1,” and thus support a body without immersion problems of water only. This specific gravity, greater than “1”, allowed the patient to lay in the solution and be supported up the body sides to an optimum immersion point. If the specific gravity is too high, excess pressures can be exhibited as area of support is drastically reduced. Keeping the mixture sufficiently fluidic presented a maintenance problem that led to patient disuse.

Patent '647 also addressed shaping of the container to reduce the contained mixture volume and of a tubular top bladder as a stiffening method of the upper surface of contained fluid for easier patient transfer or performing dressing changes.

Thompson, U.S. Pat. No. 4,357,722, demonstrates a flexible open mesh approach in a special bed frame to support the patient interfacing medium to change tension of support under various portions of the body.

Hargest et al., U.S. Pat. Nos. 3,428,973 and 3,866,606, used fluidized beads to create a specific gravity greater than “1”. These beads were micro-balloons approximating 100 microns in diameter and were “fluidized” by an air plenum chamber placed at the base of the beads separated by appropriate filtering and restrained to remain adjacent to the patient by another optional filter. Fluidization depends on the pressure drop across the supporting beads and that of the filtering system. Excess drop reduces fluidization, increases heat loss and can create ballooning of upper cover. It is thus necessary to adjust pump flow to match patient needs and size.

Lacoste, U.S. Pat. No. 4,481,686, controls bacteria through bead selection.

Goodwin addresses support of beads in U.S. Pat. Nos. 4,564,965, 4,672,699 and 4,776,050, with sequential diffusion of beads in U.S. Pat. No. 4,637,083.

Viard in U.S. Pat. No. 5,402,542 demonstrates use of a programmable EPROM and heat exchanger to control bead system component temperatures.

River sand has also been used in place of beads and periodically “fluidized” with marginal success.

Yet another approach that may be considered somewhat fluidic is the use of gel and air wherein a semi fluid gel is used in place of the fluidic bead systems in much thinner beds than the units discussed above. Due to the nature of the gel, however, its accommodation of high forces is somewhat limited.

2. Use of Polymeric Foam Such as Polyurethane

Flat Stock. Polyurethane is formed through the mixing of different polymers under controlled conditions. Some manufacturers provide the fabricator with huge blocks of foam, which are then cut into required sizes and sold to various fabricators of furniture, mattresses and so on. Some of this stock is sold as-is, or as a finished item when placed within some acceptable cover consistent with industry requirements. Some foam is rigid and some flexible.

Flexible foam acts somewhat like a spring. It is well known that the further a spring is compressed the stronger is the resisting force of that spring, and so it is with foam. The unfortunate part of this foam as a support media is that the human body is not flat and hips protrude further than waists. Accordingly, when one is side lying on foam, the hip sees more spring-back (foam fightback) or a higher load than the waist. The hip bone (Trochanter) is poorly vascularized, and thus the tissue at its surface can be robbed of the desired blood to keep the tissue healthy. Thus, the enervated person is unaware of the damage being incurred with this load, the tissue dies, and the result is a sore where the skin integrity is forever damaged without surgical intervention. Other parts of the human body, e.g., the posterior heels, malleolus (ankles), iliac crest (pelvis), coccyx (tailbone), ischial tuberosities (sit bones), scapula (shoulder blades), occiput (back of head), elbows and ears are areas that are also poorly vascularized and prone to breakdown with small loading of tissue in these areas.

Those with normal sensation and mobility feel this excess tissue load as a discomfort and responsively move away and thereby restoring circulation in that region. It has been clinically noted that a sleeping person will normally move more than twenty times during an eight hour period on a so-called “standard mattress.”

Thus, flat stock foam, using current technology, is not very desirable for patients at-risk of tissue breakdown or for their comfort. Some materials tend to give way with applied load as in the case of materials used for the Apollo astronaut couches. However, this material, known as “visco-elastic” foam, is expensive, temperature sensitive, heavy, flaky, tends to tear readily, and was not generally used by the bedding industry in the past.

Flexible polyurethane foam has been the material of choice recently. These materials are available in many densities and Indention Force Deflections (IFD). Densities may range from the soft 1.1 pounds/cubic foot to about 7 pounds/cubic foot and an IFD range of about 14 to 180 is commonly used for bed support purposes. These foams are generally manufactured as a polyether, polyester, high resiliency or other foam, with all exhibiting different characteristics. The polyether materials are generally found in furniture, while the polyester is used in packaging requiring fire resistance, while high resiliency may be found where continual cycling is encountered. Other foams also include rubber and other compounding, which have not found great favor in the bedding/cushioning industry.

Although combinations of many of these foams is common knowledge in the industry, polyether material is less expensive and it may be found in products where replacement is no problem or where material is not used extensively. Its durability under continual loading has been less than desirable.

Cut or Shaped Foam Stock. Reducing forces encountered in flat stock of polyurethane was obtained through reduction of a foam support in the bony areas by cutting the foam in a special pattern, known by the name of “surface technology”, as proposed by Rogers (the inventor herein) in U.S. Pat. Nos. 3,885,257, 3,866,252 and 4,042,987. Others also cut foam as disclosed in U.S. Pat. No. 3,828,378 by Flam, U.S. Pat. No. 4,901,387, by Luke and later U.S. Pat. Nos. 5,025,519 and 5,252,278 by Span. Kraft in U.S. Pat. No. 4,679,266 simulated foam support by zones of inner (mattress) springs with varying strengths.

Murphy in U.S. Pat. No. 4,628,557 and Rogers (inventor herein) in U.S. Pat. Nos. 4,042,987 and 4,903,359 could make a selection of foam removal under affected areas of the patient, and in Rogers' case, overloaded adjacent support members rolled automatically into the vacancy to spread load gradually to adjacent areas.

Bony areas of the body can be free of all force in foam products through use of material cutouts in mattresses, mattress replacements, body conforming supports or cushions. However, shearing forces at the demarcation edge of support and no support are a harbinger of tissue death, unless that demarcation is gradual and can be overcome by the body's internal blood pressure without creating total occlusion of the blood supply. It is then of paramount concern that proper shaping of the edges of regions where foam is removed is built into any design of a support surface so that loading is transferred gradually to adjacent support areas of the body more amenable to the applied forces (putting the load where the body can tolerate it). Some methods to do this are disclosed in U.S. Pat. Nos. 5,127,119 and 5,048,137 by Rogers (inventor herein). Foam is cut away from bony areas and edge or shear effects are accommodated by cutting foam around the removed foam area to create supporting foam forces “normal” to the body and give a gradual buildup of load over a reasonable area where blood flow is not compromised. One patent discloses technique of load spreading through shaping of the cutout conically or approaching a bell shape and consideration must also be given to packaging of delicate instruments, fruit, etc.

Convoluted foam, initially used in anechoic chambers, is formed from flat stock put through a convoluting machine, and has been used as a mattress or pad where the patient is supported by a number of peaks and valleys, such as described by Schulper, in U.S. Pat. No. 3,197,357. This machine can produce two products 4″ thick from one five inch piece of foam. Obviously, material is spread equally between the two halves in such a manner as to create a peak of four inches with valleys to offset the adjacent peaks, a type of “mirror” image.

Peak sizes were varied, as well as depth of valleys, in an attempt to equalize forces without complete relief of affected areas. In some instances, manufacturers cut the peaks off some of these convoluted pads in an attempt to control support load distribution in a more acceptable product, as the peaks were of little support value and foam was wasted. Most of this type material was fabricated from inexpensive foam and has been banned from use in many medical facilities across the U.S. This is because of its inability to eliminate damaging forces on body tissue when the user had expected more protection than the material could provide without extensive forming, cutting or having its performance completely modified as disclosed in the subject patent.

It should be noted that the so-called “visco foam” designed for NASA and being more aggressively marketed now, can be significantly improved with the present invention as its spring-back can be eliminated on demand by the user. Water beds, on the other hand, must have sufficient strength in their membrane to hold a person out of the water (and thus create pressure points) with the membrane, else the user would sink to the bottom because of most body's greater than 1.0 specific gravity .

Replacing water with “oil-well” drilling MUD, with a specific gravity of 2, was proposed by Dr. J. Reswick. This would allow a person to actually float, and if a soft interfacing material was used to separate the user from the MUD, pressures were optimal. However, the concept proved to be impracticable to institute for various reasons, one being that the MUD was a severe handling problem during shipping, and weight was another.

SUMMARY OF THE PRIOR ART

From the foregoing, it is clear that many different approaches have been used in an attempt to reduce discomfort and injury in a bedridden patient. Such discomfort and possible injury is a direct result of the stress concentration created by the non-uniform shape of the human body. An ideal supporting structure would distribute the forces due to the body weight in a way to minimize or eliminate any localized concentrations of stress, particularly shear, such as would occur at a discontinuity in the underlying material. Fluids, gels, air and such may give an overall uniform support. However, as shown in U.S. Air Force studies, even this approach gives discomfort to the seated person as interface pressures exceed the popular interface pressures of 32 mmHg and portend of potential tissue trauma.

Where bony structure in the body is near the surface and not protected by a reasonable thickness of soft tissue, an effort should be made to greatly reduce or even to eliminate the stress in that region, compensating by slightly higher forces elsewhere, where the body can tolerate it. Total elimination of stress locally is particularly important to promote healing where a bedsore or injury already exists so that the affected site can be readily supplied with a healthy flow of blood. This same rationale applies for all sites of the body where blood flow may be compromised by an inappropriate body support medium, such as would occur at not only the discontinuity of the inner support material within the mattress or cushion say, but also that major consideration always overlooked in the past, the material between the inner material and the actual tissue of the body being supported. This may come in the form of “fire barrier” material or the actual outer covering of the inner material normally ascribed to as the “mattress cover”. If this interface material is unforgiving in the worst case, all of the inner core characteristics can be masked to such an extent as to completely negate the efforts given by surface technology shaping and such. In this case, each component may perform well on its own but lacks the conformance needed to optimally perform in concert with other components and protect tissue as initially intended. However, with correct design of singular items, the correct symmetry can be attained to perform as needed collectively. This requires consideration of not only the immediate support medium but also the major support structure, such as type of chair, spring or stainless steel sheet bed and such.

Similarly, packaging of complexly-shaped products to be shipped from one location to another has created a special marketplace for special support media, such as “foam-in-place”, air cells and so on. The present invention addresses this need as well because the packaging of people is no different to packaging components or products—its a matter of degree, as all must be protected from the outside environment where their integrity is challenged. Another reason for including this aspect of protection is to conserve use of oil and forest-related products and help keep the economy in check as the proposed interface protection media can be re-used for reshipping over and over again and the proposed mattress and seat cushions keep much of the environment away from the foam and thus extend its life substantially.

The prior art has not as a rule directly addressed these goals. Although it has been generally recognized that a support structure for the human body needs to provide different stress patterns in different areas, as do delicate instruments, most schemes do not fully achieve it. In fact, some have discontinuities in material and make no apparent attempt to minimize shear stress at those points. Again, similar to the packaging of products such as glassware, arriving at a destination, broken.

SUMMARY OF THE INVENTION

This invention relates to the support of a person in the prone, supine, side-lying, semi reclined or sitting position without the usual stress concentrations that may lead to tissue trauma, decubitus ulcers, ischemic ulcers, or bed sores, and is extended in its concepts to the shipping needs of delicate instruments (positioning, cushioning and impact protection) and other items of concern. It is also an object of the present invention to provide support for a human body in a manner so that the forces of support have fewer concentration points which are likely to occur at or near bony prominences, nerves or tendons and which, if not accommodated, can lead to serious complications, such as ulcers, nerve damage or strained muscles, tendons and other disabling factors.

This invention addresses the stress distribution problem by combining several techniques. First, using a basic foam inner material, or other material that gives a similar performance, the invention provides regions where material has been cut in some selected manner, placed adjacent or in concert with dissimilar material, or the same material with differing support characteristics, cut away, omitted, or formed to reduce the magnitude and abruptness of any stress concentrations when supporting a body (collectively or alternatively: “foam force accommodation zones”). This technique is then combined with the process of applying a membrane (“enclosure member”) of appropriate warp and weft to assure appropriate force distribution is applied to the supported surface should cavities be located under the membrane and over the insert material to smooth out the localized variation in stress and concomitantly, if the membrane is able to control the amount of air or fluid surrounding the space between the bladder and interstices of the foam, the fluid pressure may be varied to change the characteristics of the foam itself.

This latter components or aspect of the invention can be characterized by reviewing U.S. Pat. Nos. 5,127,119 and 5,048,137 by the present inventor and observing that when the described foam structures were loaded by a body, the foam will “fold” over in a normal direction to the tissue of the body to reduce the shearing occurring at the tissue. (By looking at a cross-section of the conical shape as discussed herein, a linearized “back-sloping” across a surface edge has a much more efficient pressure/shear distribution than the so-called “waterfall” cut.)

Notably, if a bladder were to be placed between the body and supporting foam of the nature just described, the bladder, with air or fluid control ability, can hold the foam (of the linearized cone edge) in its desired place and virtually create a minimal interface differential force, much as is found when floating in water.

By considering all the requirements for patient care ranging from personal hygiene to “chucks,” to diapers to sheets, to mattress covering to sweat collectors, to fire barriers to support medium, to the underlying support, the present invention has evolved to give the patient protection as well as comfort. “Comfort” has been shown to be directly related to forces exerted on the body by Rogers, as previously mentioned in the “Hospital Materiel Management Quarterly” article, “Body Support Testing and Rating,” dated August 1992.

Many inventors and developers of products have been diligent in their detailed design of products, as seen from within the confines of a designer's view without the clinical experience seen by the inventor (substantiated by reports from University of Southern California School of Rehabilitation Engineering Center at Rancho Los Amigos Hospital (California) Annual Reports of progress, CV Mosby Orthopedic Atlas, and being Director of the U.S. Army Field Medical Laboratory fabrication and numerous technical articles) to adequately formulate a suitable set of specifications gained from experience in the clinical care of patients as well as in the design of delicate instrument shipment, such as those encountered in a U.S. Army Field Medical Laboratory. With this background, the present inventor hereof expands on the objectives of this invention to include patients' well-being, as well as handling of delicate equipment and as such, emphasizing that a major objective of the invention is to improve on the many available products, followed by details of collective specifications of previous patents, mingled with personal experience and coalesced into new “Definitive” mattresses, upgrading of past patents and designs, cushions and the supporting structures for handling delicate products.

In view of the foregoing, it is an object of the present invention to provide an improved mattress enclosed in a functional membrane.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that upgrades existing equipment performances to better meet the needs of consumers and patients

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that can be used for patient support, tissue protection and comfort whether seated or laying down.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that clears the sacrum, coccyx and ischial tuberosities of pressure and shear when required by raising the supported person sufficiently to clear pressure points on their body.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that also incorporates alarms, if so needed, to indicate when tissue is being overstressed through built-in sensors.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that has nearly zero interface pressure/shear over the potentially affected site.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that extends the life of the contained foam within a support system by isolation from the local environment.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that allows easy storage and shipping with its self-contained pumps able to be vacuum packed without external pumps or the like.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that can cost-efficiently cover existing mattresses/cushions with portions of the present invention for low cost upgrading of equipment and service cost reduction.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that can control time constants and damping ability of foams, springs of all shapes in spring mattresses and seating to meet the goals of the original designs through compression and expansion of fluid medium surrounding portions, or all of the existing equipment.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that can assess tissue loading by measuring pressure and shear under the bony prominences without any additional equipment to the mattress or cushion which, in turn, will allow one to take the corrective action with built-in features of the existing equipment.

It is another object of the present invention to provide an improved mattress enclosed in a functional membrane that only requires one person to readily move a patient via the built-in transfer sheet.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that also correctly positions patients with self contouring body supports.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane with the ability to self vacuum pack the position of patient or when being transported from one location to another.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that gives the user even more fluid-like support through use of judicious control of fluid surrounding this foam mattress or cushion by use of an enclosed cover and suitable operating means to control the internal environment.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that can complete foam return by scaling closure of a twist valve marked for time constants or rates of response.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that includes the option of time constant changes, or the direction of flow to and/or from the mattress at a controlled rate or all by valve control at user option.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that can vacate or inflate the present invention through twist valves in tandem or unitarily.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that allows the user selection of one, three or five valves, joined integrally with the supported member to improve overall performance needs.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that allows the use a remote plug-in attachment integral to the support surface.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that uses an outside source of energy to operate its functions.

It is another object of the present invention to provide an improved mattress or cushion enclosed in a functional membrane that can be controlled remotely through suitable RF or RF-like coupling.

It is another object of the present invention to provide an improved mattress, cushion, packaging enclosed in a functional membrane that can also be used as partial reusable packaging around a product that can perform well with varying time constants tied to springs for buffering at required frequency of vibrations expected during transit.

It is another object of the present invention to provide an improved mattress or seating enclosed in a functional membrane that can provide a seated driver or passenger in a vehicle with a variable time constant support, much as the variable dampers are tied to the chassis of a vehicle to assist in smoothing out the chassis vibrations encountered over various terrains.

In satisfaction of these and related objectives, the present invention overcomes the stress distribution problem unlike anything available by combining several techniques. A basic foam inner material is specially cut to reduce the magnitude and abruptness of any stress concentrations when supporting a body. A membrane of appropriate warp and weft is applied to the supported surface to smooth out the localized variation in stress while the fluid pressure may be varied to change the characteristics of the foam itself and the under-support structure designed to assist in meeting these ends.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the concepts of tissue trauma or tissue death.

FIG. 2 is a detailed description of drawings for design of a cutout.

FIG. 3 illustrates the function of a simplistic approach to a difficult problem—care of the hospitalized, elderly or bed-ridden patient.

FIG. 4 illustrates cavity function with loading and vacuum control.

FIG. 5 illustrates the pressure/shear transducer.

FIG. 6 illustrates three versions of the invention for general use with mattresses, cushions and shipping fragile goods with a reusable cover or “shipper.”

FIG. 7 illustrates a detailed operation of the self-contained pump action.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, the concepts of tissue trauma or tissue death is illustrated. Foam compression has a varying, and often times subjective result to people as an identical compression or cushioning feels “hard” to some and is acceptable to others. Mattresses or cushion are generally accepted by “feel,” which relates to peak pressures as illustrated in FIG. 1.

Part (a) illustrates a slab of foam (1). Part (b) shows a body (2) loading foam (1) to a height of (3). Part (c) shows a heavier body placed upon the same foam which compresses to where equilibrium has been reached. However, in part (d), with a heavier, load there is only a thickness (5), depicting a possibility of “bottoming-out”. This term may be a misnomer, as the foam may not have bottomed out as it could have been compressed a small amount more before all elasticity of the foam has disappeared and only the physical cell mass is supporting the load (2). Part (e) illustrates a bony body (6) being placed upon a similar foam block (1) and the resulting forces are (7) where the bone (9) is penetrating the tissue and causing shear forces (8) up the side of the bone. This force can be shown to be the directly related to the peak pressure (12), while the additional shear load at the tissue surface (11) and the surface tension (10) also contribute as shown in the next part. Part (f) depicts the breakdown of tissue at the surface (13) but the majority of damage is at the bone demonstrated by (14).

These are the forces that restrict blood flow and are the start of the insidious ischemic ulceration previously discussed. One of the primary objectives of the present invention is to prevent these causes of tissue failure.

Referring to FIG. 2, which is a detailed description of drawings for design of a cutout. In FIG. 1, the effect of sharp edges or difference between support and no support results in high shear forces to a body. In FIG. 2, the body is placed over a shaped cutout which can be a cone in cross section or a straight edge into the drawing. When the edges (3) of the foam (1) and a cutout (2) are loaded by a body, the edges roll inward as at (4). This gives more surface area of support so the load at (4) is spread over a greater area than if the walls of the cutout were straight (greater area for load, the less pressure at the site of support), or even cut inward and the forces tend to be normal to the cutout at (4). This, in turn, reduces shear at the bone and the perpendicular or peak pressure loading (5) is also reduced creating a safer environment of force control and also resultant comfort.

FIG. 3 illustrates function of a simplistic approach to a difficult problem—care of the hospitalized, elderly or bed-ridden patient. The shaped cone of the inventor's prior patent has led to the use of the sloping backward method of edge control of shear forces on the body adjacent to the coccyx/Trochanter areas of support in a mattress, cushion and sensitive areas of body support.

A person's trunk section 1 is shown placed on the support 27. 2 is the leg section and it also is placed on the support 27, which may consist of strong corrugated cardboard for low costing that can consist of two adjacent panels which are bifurcated longitudinally to allow rolling of the supported mattress or cushion or in the case of the mattress, allow “gatching” of the bed (and supported mattress) while giving the back support, clearing the coccyx and ischial tuberosities of the patient and allowing positioning of the legs independently. 3 is the foot pillow attached by hinge 28 to the main cover of Dartex like material also used over 2 as in 1. 4 is the outer edge material as is 15 with a cavity in between and below, to support the use of the collector 24 fitting within the sloping cavity between the two names sections. 5 is the rolled or folded transfer sheet attached to the cover 7 and the leg covering. This sheet is folded back onto itself for the patient to be rolled upon and when in place, sheet is pulled along with the patient for transfer to wheelchair etc. 6 is a sensor shown in following figure. This sensor can be built into the cover or be separate item. 7 is outer fluid proof material that is vapor permeable (thus the need for the sweat collector introduced through the double Ziploc type fastener) that allows moisture to enter the inside foam if not protected. Material is RF welded on all edges to assure fluid proof integrity. 8 is the self-inflating pillow attached by hinging to the cover material. The pillow covering will also be similar to the main cover except more flexible. The pillow will be filled with particulate material of choice so that it can also be vacuum controlled, fluid inflated or time restrained compression to meet patient/ physician needs. 9 is the hinge attachment to the cover. 10 is the valving discussed under the self-inflating description in following. 11 is the pillow deflated and positioned over end of bedding. 12 is the vent control section of the pillow described in the following also. 13 is the inflated pillow. 14 is already covered. 15 is the end filler of the cavity between the head and leg portion of the support system. 16 illustrates the back-sloping edge of the cutout running laterally across the mattress for pressure/shear relief of the Trochanter- coccyx-sacral area of the body fitting over cavity 30. 17 are valves for controlling the positioning and function of the rotated foot piece 21 hinged at 28 and now used for knee resting shown dotted. 18 is the pillow-leg portion in the knee support position. 19 are valves as in previous sections to control the time constant, vacuum forming or inflating ability of the various portions of the Definitive mattress. 20 shows the same unit pushed up in place and held there by the hinge 28 and particulate material fluid vacated to form unit to feet if needed. 21 is foot pillow position for normal foot control as needed. 22 notes the valve positioning. In smaller units one set of valves will be quite adequate although all will perform well when appropriately designed to match production needs. 23 is hinge point in base unit if it is hard material and will not flex on its own. 24 is collector of waste material that can be removed from under patient when appropriate. 25 is a self inflating pillow for positioning collector or it can have added feature of filling the vacant space 30 if collector not used. 26 is pneumatic sensor for measuring peak pressure/shear in a novel inexpensive way described later. 27 is the composite baseboard previously mentioned. With patient in place on the Definitive mattress the buttock portion of the body will be free of support due to the cavity 30 in which the collector is placed. 28 is hinged portion of pillow 3. 29 is another Ziploc for placement of stiffener to assure the vacuum aspect pulls down under the patient rather than allow vacuum to also raise bottom of cavity unless this aspect is used to raise collector 24 and pull down covers over modules 1 and 2 when jointly connected through pillow 25 or over baseboard 27. See following figures for this detail of action. 30 is the cavity over which the buttock portion of a person is placed and in which area the effluent is caught by collector 24. It becomes obvious that the catch area of this cavity is also the bony area of the body more prone to tissue death if overstressed.

The mattress can be pneumatically controlled by valves at 22 to any degree needed by patient. More vacuum and the more the edges at 26 will fold into the cavity giving more relief or used to reduce back pain in some.

The head can be elevated rotated and controlled with softness dictated by inflation level of unit. The knees can be elevated through use of the rotating foot/leg unit and molded to the body shape require while unit is pumped on the side. If the unit is to be stored or shipped, it can be folded back on itself, both sections vacuumed by their self-contained units and unit moved.

FIG. 4—Cavity function with loading and vacuum control. As previously illustrated, the back cut top edges of the foam cavity are initially in position 1 when unloaded and cover 4 spans the gap. When a load W is placed on the cover and cavity the foam rolls down to position 2 with the cover also being forced down into the cavity. However, when a vacuum is applied to space 7 and the surrounding foam, the foam and cover 4 is now pulled down into position 5 creating a gap 6 under the loaded site. This is where it is feasible to have zero interface pressure under a bony site, such as a trochanter and the shear forces are now spread over the gently curved area of the foam without the foam spring force in place. Thus, this creates a pseudo fluidic type of support at the tissue interface.

FIG. 5—Pressure / shear transducer. The unit illustrated is an integral part of the Definitive mattress where indicated for patients with potentially compromised tissue. As a stand-alone unit, it consists of two layers of highly flexible fluid-proofed material with little or none surface “stiction”. In its preferred embodiment, the unit is RF welded in the form shown with the outer envelope 1 and the internal divisions 2 creating a maze type of path to be placed under a suspected site of concern on a patient's body.

Air is introduced in preferably “burst” manner or step function. When air is noted coming out of the unit the amount of air applied at the inlet for this to happen gives the interface forces under which the unit is being subjected.

Calibration of the unit requires demarcation between pressure and shear by using standard weights to close off one part of the maze. It is obvious to those skilled in the art of air flow to see that if the unit is highly flexible it will see not only the pressure involved but also the shear occurring at the site of monitoring. This is unattainable with standard sensors with discrete elements tied together as the measurements in this instance are clouded by sensor placement relative to each other, flexibility of carrier and potential cross-talk between sensors.

The sensor of the present invention is unique because of its minimal expense as an individual sensor, but also because of its suitability to be included in the covering of product without affecting product performance. The air supply, switching and monitoring gauges are omitted as they are common to those involved in instrumentation methods.

The transducer can be part of the cover design as its interference with system function is minimal and its usefulness far outweighs any loss of motion to the covering. Monitoring can be by RF link to a station or to attendant or by a simplistic visual indicator that is hand held or part of the bed. In the preferred embodiment, automatic sequencing of air bursts can be self-contained in a hand held or remotely located unit in a number of ways commonly known to those who design such devices.

FIG. 6—“Fits-all” covers. FIG. 6 illustrates three versions of the invention for general use with mattresses, cushions and shipping fragile goods with a reusable cover or “shipper.” Illustration A is for covering existing mattresses to make them more functional and without having to replace existing mattresses because the cover is ripped, torn or unusable or the mattress itself can have upgraded performance in preventing tissue trauma or improving comfort of the user.

Liners of foam can be placed inside or be added while inserting mattress. 1 depicts the foot section as discussed in foregoing. With its hinge to cover 5 if needed for particular application of foot drop, cavity filling a foot handling as in the Definitive unit of FIG. 3 or knee elevation. 2 is Ziploc for mattress insertion. Fitting a mattress into a cover can be problematic. However, the subject invention cover herein being discussed is not necessarily a standard cover, as it can be oversized and surplus (minimum) tucked under assembled item. 3 is pillow with its hinge to 5 and 4 are the controls with functions as outlined in previous disclosures herein. The unit is highly flexible and shipping and handling are satisfactory as all air can be vacated by using outside pressure on package and closing the metering valve. “B” is similar to “A” with the control remote as discussed previously. “C” is the cushion and packaging module sized as needed with Ziploc probably on underside for the seat cushion.

It should be noted that the Ziploc type structure must be fluid proof under pressure differential or it will not be suitable for vacuum of any extent before its feature is negated.

For cushion use the unit should be sized appropriately as tucking excess on underside may be suitable for a mattress but problematic for commercial or office use. When the unit is made in factory with sizes established the completed item may be welded in place for function and appearance. Ziploc length and positioning is critical for easy assembly or additional filler will be provided as an extra for appearance.

Pumping elements needed can be by specification. If no pumping-up is needed, then one function can be omitted and only three valves used or at minimum two. Packaging units are fabricated much like a Ziploc itself or one of the items marketed for storage of clothing. However, this unit has a self contained pump and vent as well as added air if necessary for additional impact protection.

Cushions can be assembled to be controlled by the same process as the mattress described. The user can deflate/inflate by compressing any part of the cushion with valving appropriate to need activated as discussed in the following explanation of pump operation. A sensor can be included when bottoming is about to occur if a cutout is used. The client then replaces the cushion after emergency inflation. A timer function can also be included with a pneumatic option to assure time of sitting has expired.

As for positioning and support products, as previously mentioned, all the separate units now in use can be made more effective in function, extend their life and reduce costs by including appropriate valving and sloping of support surfaces at areas of concern to include consideration of design with all or part of the invention as needed to include those to be considered as a minimum head, body, arm, leg and foot positioners (with safer support), operating room table pads, gurney pads, wheelchair inserts, wheelchair cushions and pillows.

FIG. 7—detailed operation of the self-contained pump action. The top figure for the self-contained pump concept illustrates a typical concept for the self pumping of fluid in, out and metered. #1 is outer fluid-impermeable bladder or cover for enclosed mattress/cushion/other #4. #2 is self-inflating inner bladder adjacent #4. #3 is second self-inflating bladder adjacent #4. #4 is main mattress that could be plain foam, textured foam, convoluted foam, batting, sliced/diced foam, surface technology applied to foam surface performance, contoured shapes, irregular shapes of varying densities (spring-back) and demarcations, springs (flat, coiled, conical and such) other fluidic components in various shapes for demarcation control. #5 is metering twist valve (or other able to adjustably meter flow) for altering #4 response time and spring constant by modifying flow through cavity #12 and surrounding areas and interstices of #4. #6 is twist valve (or other to be able to finitely control fluid flow) is for metering and controlling flow out through its related one-way valve #8, its self contained foam cavity surrounding #2 with its enclosing fluid impermeable membrane with fluid entering one way valve #10 for control of egress of fluid #12 from around and through #4 and exiting at one way valve #8 and metering twist valve #6. This action evacuates fluid from within enclosure #1 and mattress/cushion #4 by compressing combined unit at position #12 above #2 & #3 with #5 and #7 closed. This allows the attendant or user to adjust amount of fluid that is vacated around #4 to such an extent that fight-back of #4 is removed or actually overcome to extent of compressing #4 in its entirety. # 7 is a metering twist valve (or other able to adjustably meter flow) allowing air to enter its associated one-way valve #9 through foam #3 and exiting through one way valve #11 to cavity #12 with #5 & #6 closed. This allows the fluid to enter by the amount needed by user to give a combined inner control plus its surrounding fluid to reach a level of comfort or height needed for various reasons.

In summary, close valve numbers 6&7 and use Valve #1 to change inner component #4 to respond as rapidly or as slowly as needed by user. Close #5 & #7 and open #6 to expel contained fluid #12 to compress around #4 and where #4 has been contoured or cut in some manner to give a varying force support topography, the weaker sections will collapse first so that absolute clearance of a supported body, be they seated or laying down, can be obtained through pumping the foam located in an unused portion of the support surface such as the corner of a mattress or cushion (Note the unit may be mounted sideways for cushion or other action if top compression is not suitable.) Closing #'s 5 & 6 and opening #7 allows fluid to enter the enclosed structure and pumped in a similar manner as when evacuating, will allow fluid to enter at a rate and amount suitable to the user who may wish to have the fluidic feel to their support or allow person to raise themselves to a different working level for comfort or function.

The lower figure of FIG. 7 illustrates one method of remotely controlling the function described above to be removed from the actual support surface. The following describes one method of direct physical linking to the surface to be controlled but it can be readily understood that such functions can be duplicated through an RF type of interconnect to self contained units mounted suitably around, or in, a surface requiring control as described herein. It is also another method wherein Hospital air vacuum and pressure sources could be connected directly with associated circuitry to remotely control bed/mattress/wheelchair surface support functions. The unit #9 can contain its own pumping section, as described in previous figures where valves # 1, 2, 3, 4 and 5 replace #5, 6, 7, 8, and 9 with valves 10 and 11 selectively placed in portable unit or in the unit under control, or where vacancy #12 occurs. #6 & #7 are self priming pumps as previously described with tubing such as #8 collectively operating through #10 on to quick disconnect #11 attached to the body under control.

Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limited sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the inventions will become apparent to persons skilled in the art upon the reference to the description of the invention. It is, therefore, contemplated that the appended claims will cover such modifications that fall within the scope of the invention. 

1. A pressure gradient dampening apparatus comprising: a foam body, having one or more foam force accommodation zones formed at pre-selected selected positions to accommodate and dampen forces applied respectively to said foam body at or near said one or more foam force accommodation zones; an enclosure member which is reversibly, substantially impermeable to gas and fluid, and in which said foam body is enclosed; valve means interface d with said enclosure member for permitting introduction of an inflation medium into, or exhaustion of an inflation medium from an interior space of said enclosure member to impart said reversible, substantial impermeability to said enclosure member; pump means, interfaced with said valve means for facilitating said introduction of an inflation medium into, or exhaustion of an inflation medium from an interior space of said enclosure member.
 2. The apparatus of claim 1 wherein said foam body comprises multiple, separate foam components, and wherein said enclosure is constructed to have multiple, separately sealed chambers in at least some of which chambers said foam components reside, and wherein valve means are independently operable to separately introduce an inflation medium into, or exhaust of an inflation medium from an interior space of each said chamber of said enclosure member. 